It is known to fit a wheel of landing gear with a braking device. It is also known to fit a wheel of landing gear with an independent drive device mainly comprising an electric motor so as to be capable of moving the aircraft on the ground without assistance from its thrusters.
Such devices are found to be bulky, which makes it difficult to fit a given wheel both with a braking device and with an independent drive device. Proposals have thus been made to fit some of the wheels on a given undercarriage with braking devices and other wheels with independent drive devices.
Nevertheless, that arrangement reduces the braking capacity of the aircraft compared with an arrangement in which all of the wheels are fitted with braking devices only.
Similarly, that arrangement presents reduced capacity for independent drive of the aircraft, since not all of the wheels are fitted with independent drive devices.
That drawback is made worse when the state of the ground leads to reduced coefficients of friction, e.g. in the event of rain or ice.